In the 4th Generation wireless communication systems, MIMO schemes play a fundamental role in order to achieve high data rates in the downlink.
Multi-Input Multi-Output (MIMO) technology improves efficiency of data transmission and receipt using a multiple transmit antenna and a multiple receive antenna.
While a receiver receives data through a single path if a single antenna is used, a receiver receives data through multiple paths if a multiple antenna is used. Thus, speed and capacity of data transmission is improved and coverage is enlarged.
Generally, there are an open-loop MIMO system in which a transmitter doesn't use feedback information from a receiver and a closed-loop MIMO system in which a transmitter uses feedback information from a receiver in multiple antenna systems. In a closed-loop multiple antenna system, a receiver transmits channel state information or channel state indication (CSI) to a transmitter and the transmitter detects channel status through it so that performance of a communication system is improved.
Implicit recommended transmission properties (e.g. CQI/PMI/RI) feedback and explicit CSI feedback are two representative feedback schemes, in which CSI feedback is categorized into quantization CSI feedback and analogue CSI feedback. Channel matrix H or covariance matrix R could be the feedback information in the CSI case. For more efficient transmission, noise variance (e.g. interference level) is transmitted to a transmitter together with channel matrix H or covariance matrix R.
In a method of transmitting and receiving of CSI feedback according to the related art, a receiver transmits analogue values of channel matrix H or covariance matrix R. Thus, the Peak-to-Average Power Ratio (PAPR) is increased.